Criteria

• Adding conditions to Criteria
• Retrieving partial object with the help of Projections

Criteria :

• Using criteria we can only retrieve the objects from the database. We can't perform DML operations.
• And with criteria we can retrieve complete object only. We can't retrieve partial object.
• To retrieve partial object we have to combine criteria with projections.

• To execute Criteria first we need to create Criteria object.
• To get Criteria object, we need to call createCriteria() method on Session interface. We need to pass our pojo class to this method.
• On the query object call list() method , list() will return java.util.List.

Criteria criteria=session.createCriteria(Employee.class);
List list=criteria.list();
Iterator iterator=list.iterator();

while(iterator.hasNext()){
Employee emp=(Employee)iterator.next();
}

package com.beans;

public class Employee {
private long employeeId;
private String employeeName;
private double salary;

public long getEmployeeId() {
	return employeeId;
}
public void setEmployeeId(long employeeId){
	this.employeeId = employeeId;
}
public String getEmployeeName(){
	return employeeName;
}
public void setEmployeeName(String employeeName){
	this.employeeName = employeeName;
}
public double getSalary() {
	return salary;
}
public void setSalary(double salary) {
	this.salary = salary;
}

}

<hibernate-mapping>

<class name="com.beans.Employee" table="EMPLOYEEDB">
  <id name="employeeId" column="EID"/>
  <property name="employeeName" column="ENAME" length="30"/>
  <property name="salary" column="ESAL"/>      
</class>

</hibernate-mapping>

<hibernate-configuration>

<session-factory>

<!-- Related to the connection properties -->

<property name="myeclipse.connection.profile">myJdbcDriver</property>
<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@localhost:1521:xe</property>
<property name="connection.username">lms</property>
<property name="connection.password">scott</property>

<!-- Related to the hibernate properties -->
<property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">update</property>

<!-- Related to hibernate mapping -->
<mapping resource="com/hiber/Employee.hbm.xml" />

</session-factory>

</hibernate-configuration>

Client Application 1 :

package com.client;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

import com.beans.Employee;

public class ClientApp {

public static void main(String ar[]){

Configuration cfg=new Configuration();
cfg.configure();

SessionFactory sf=cfg.buildSessionFactory();
Session session=sf.openSession();

Criteria criteria=session.createCriteria(Employee.class);
List list=criteria.list();
Iterator iterator=list.iterator();

while(iterator.hasNext()){
Employee emp=(Employee)iterator.next();
System.out.println(emp.getEmployeeId());
System.out.println(emp.getEmployeeName());
System.out.println(emp.getSalary());
}

System.out.println("success");
}

}

Adding conditions to Criteria :

• Using Criteria if we want to add conditions to the query, then we need to create one Criterian object and add this object to Criteria.
• To add Criterion object to Criteria, we need to call add() method on criteria object.
• To create Criterion object, we need to call static methods of Restrictions class, each method of this class returns Criterion object.

Criteria criteria=session.createCriteria(Employee.class);
Criterion criterion=Restrictions.gt("salary", new Double(3000));
 //here salary is pojo class variable name
criteria.add(criterion);

Note : POJO class, Mapping and Configuration files are same as above application.

package com.client;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Criterion;
import org.hibernate.criterion.Restrictions;

import com.beans.Employee;

public class ClientApp {

public static void main(String ar[]){

Configuration cfg=new Configuration();
cfg.configure();

SessionFactory sf=cfg.buildSessionFactory();
Session session=sf.openSession();

Criteria criteria=session.createCriteria(Employee.class);
Criterion criterion=Restrictions.gt("salary", new Double(3000));
criteria.add(criterion);

List list=criteria.list();
Iterator iterator=list.iterator();

while(iterator.hasNext()){
Employee emp=(Employee)iterator.next();
System.out.println(emp.getEmployeeId());
System.out.println(emp.getEmployeeName());
System.out.println(emp.getSalary());
}

System.out.println("success");
}

}

Note : POJO class, Mapping and Configuration files are same as above application.

package com.client;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Criterion;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Restrictions;

import com.beans.Employee;

public class ClientApp {

public static void main(String ar[]){

Configuration cfg=new Configuration();
cfg.configure();

SessionFactory sf=cfg.buildSessionFactory();
Session session=sf.openSession();

Criteria criteria=session.createCriteria(Employee.class);
Criterion criterion=Restrictions.gt("salary", new Double(3000));
criteria.add(criterion);

Order order=Order.asc("salary");
criteria.addOrder(order);

List list=criteria.list();
Iterator iterator=list.iterator();

while(iterator.hasNext()){
Employee emp=(Employee)iterator.next();
System.out.println(emp.getEmployeeId());
System.out.println(emp.getEmployeeName());
System.out.println(emp.getSalary());
}

System.out.println("success");
}

}

Retrieving partial object with the help of Projections :

• Using Criteria we can retrieve only complete object, but it is possible to retrieve partial object if we combine Criteria with projects.
• Projection is an interface and Projections is a class.
• To get Projection object we need to call property() method on Projections class. It is static method and will return Projection object.
• To add Projection object to Criteria , we need to call setProjection() method on Criteria object.
• To retrieve partial object with single column, we need to create Projection object for that particular column value type.

Note : POJO class, Mapping and Configuration files are same as above application.

Client Application 4 :

package com.client;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Criterion;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projection;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;

import com.beans.Employee;

public class ClientApp {

public static void main(String ar[]){

Configuration cfg=new Configuration();
cfg.configure();

SessionFactory sf=cfg.buildSessionFactory();
Session session=sf.openSession();

Criteria criteria=session.createCriteria(Employee.class);
Criterion criterion=Restrictions.gt("salary", new Double(3000));
criteria.add(criterion);

Order order=Order.asc("salary");
criteria.addOrder(order);

Projection projection=Projections.property("salary");
criteria.setProjection(projection);

List list=criteria.list();
Iterator iterator=list.iterator();

while(iterator.hasNext()){
Double salary=(Double)iterator.next();
System.out.println(salary);
}

System.out.println("success");
}

}

Note : if we add 2 Projection objects to Criteria then 2^nd projection will override the first Projection.

• To add multiple Projection objects to Criteria, we need to create ProjectionList. To create ProjectionList, we need to call projectionList() on Projections class.
• Create multiple Projection objects and add these Projection objects to ProjectionList. Set this ProjectionList to Criteria. To set ProjectionList to Criteria we need to call setProjection() method on Criteria object.
• Finally while iterating the list, we need to type cast with Object[] because list contains partial object with multiple columns.

Note : POJO class, Mapping and Configuration files are same as above application.

Client Application 5 :

package com.client;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Criterion;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projection;
import org.hibernate.criterion.ProjectionList;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;

import com.beans.Employee;

public class ClientApp {

public static void main(String ar[]){

Configuration cfg=new Configuration();
cfg.configure();

SessionFactory sf=cfg.buildSessionFactory();
Session session=sf.openSession();

Criteria criteria=session.createCriteria(Employee.class);
Criterion criterion=Restrictions.gt("salary", new Double(3000));
criteria.add(criterion);

Order order=Order.asc("salary");
criteria.addOrder(order);

ProjectionList projectionList=Projections.projectionList();

Projection projection1=Projections.property("employeeName");
Projection projection2=Projections.property("salary");

projectionList.add(projection1);
projectionList.add(projection2);

criteria.setProjection(projectionList);

List list=criteria.list();
Iterator iterator=list.iterator();

while(iterator.hasNext()){
Object[] values=(Object[])iterator.next();
System.out.println(values[0]);
System.out.println(values[1]);
}

System.out.println("success");
}

}